public ActionResult Create(Exercise exercise)
        {
            if (ModelState.IsValid)
            {
                db.Exercises.Add(exercise);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            ViewBag.UserId = new SelectList(db.Users, "UserId", "Email", exercise.UserId);
            return View(exercise);
        }
 public ActionResult Edit(Exercise exercise)
 {
     if (ModelState.IsValid)
     {
         db.Entry(exercise).State = EntityState.Modified;
         db.SaveChanges();
         return RedirectToAction("Index");
     }
     ViewBag.UserId = new SelectList(db.Users, "UserId", "Email", exercise.UserId);
     return View(exercise);
 }